Method for screening peptides for use in immunotherapy

Abstract

Identifying subdominant/cryptic epitopes (I) that are presented by a HLA (human leukocyte antigen) Class I molecule, is new. Identifying subdominant/cryptic epitopes (I) that are presented by a HLA (human leukocyte antigen) Class I molecule comprising selecting at least one peptide (II) of 8-11 amino acids (aa), potentially representing an epitope for Class I presentation, from a protein against which a cytotoxic T cell (CTL) response is to be raised. (II) corresponds to a non-immunogenic peptide with low affinity for Class I molecules. Variants (IIa) of (II) are prepared in which the N-terminal aa is replaced by Tyr and their immunogenicity detected by identifying those that generate a CTL response against target cells expressing the parent protein. Peptide sequences from which active (IIa) are derived are then identified. Independent claims are also included for the following: (1) immunogenic peptide epitopes (IIa) derived from (I) identified this way; and (2) nucleic acid (III) that encodes chimeric polypeptides (IV) containing one or more, same or different, copies of (IIa).

1. An immunogenic peptide epitope which is derived from a subdominant/cryptic epitope presented by HLA A2.1 by substitution of the N-terminal amino acid of said subdominant/cryptic epitope with a tyrosine residue, wherein said subdominant/cryptic epitope is chosen from:
 the peptide HER-2/neu 650: PLTSIISAV (SEQ ID No. 4) 
 the peptide HER-2/neu 466: ALIHITNTHL (SEQ ID No. 5) 
 the peptide HER-2/neu 402: TLEEITGYL (SEQ ID No. 6) 
 the peptide HER-2/neu 391: PLQPEQLQV (SEQ ID No. 7) 
 the peptide gagp24-212: EMMTACQGV (SEQ ID No. 8) 
 the peptide pol79: LLDTGADDTV (SEQ ID No. 9) 
 the peptide mhp 572: RLFFYRKSV (SEQ ID No. 10) 
 the peptide mhp 988: DLQVNSLQTV (SEQ ID No. 11). 
 
     
     
       2. A composition comprising at least one immunogenic peptide epitope as claimed in  claim 1 . 
     
     
       3. The composition as claimed in  claim 2 , which also comprises one or more other immunogenic epitope(s). 
     
     
       4. The composition as claimed in  claim 2 , which comprises a chimeric polypeptide comprising one or more copies of an immunogenic peptide epitope derived from a subdominant/cryptic epitope presented by a class I HLA molecule. 
     
     
       5. The composition as claimed in  claim 4 , wherein said chimeric polypeptide also comprises one or more copies of one or more other immunogenic epitope(s). 
     
     
       6. The immunogenic peptide epitope as claimed in  claim 1 , which is the peptide mhp 572Y1: YLFFYRKSV (SEQ ID No. 61). 
     
     
       7. The composition as claimed in  claim 2  and a pharmaceutically acceptable carrier.